Apparatus for continuously solution heat-treating aluminum and its alloys



y 1955 ARTHUR DEAN SMITH ALSO KNOWN 3,194,545

A5 A. DEAN SMITH APPARATUS FOR CONTINUOUSLY SOLUTION HEAT-TREATINGALUMINUM AND ITS ALLOYS Filed March 17. 1960 2 Sheets-Sheet 1 INVENTORARTHUR DEAN SMITH ATTORNEY y 3, 1965 ARTHUR DEAN SMITH ALSO KNOWN3,194,545

As A DEAN SMITH APPARATUS FOR CONTINUOUSLY SOLUTION HEAT-TREATINGALUMINUM AND ITS ALLOYS 2 SheetsSheet 2 Filed March 17. 1960 INVENTORARTHUR DEAN SMITH ATTORNEY United States Patent 3,194,545 APPARATUS FORCONTINUOUSLY SOLU- TlQN HEAT-TREATENG ALUMINUM AND ITS ALLQYS ArthurDean Smith, also known as A. Dean Smith, San

Lorenzo, (Ialif, assignor to Kaiser Aluminum 8; Chemieal Corporation,Oakland, Calif.

Filed Mar. 17, 1960, Ser. No. 15,766 3 Claims. (Cl. 266-3) Thisapplication is a continuation-impart of my copending application SerialNo. 664,068 filed June 6, 1957, and now abandoned.

This invention relates in general to the treatment of metals. Morespecifically this invention relates to continuously solution heattreating a strip, sheet, wire, etc. of heat treatable aluminum alloys.

The high strengths of the heat treatable alloys of alurninum, such asalloys 2024 (having a nominal composition of 4.5% copper, 0.6%manganese, 1.5% magnesium, balance aluminum and normal impurities), 6061(having a nominal composition of 0.25% copper, 0.6% silicon, 1.0%magnesium, 0.25% chromium, balance aluminum and normal impurities) and7075 (having a nominal composition of 1.6% copper, 2.5% magnesium, 5.6%zinc, 0.3% chromium, balance aluminum and normal impurities) areobtained primarily by subjecting the metals to two thermal treatments,namely, solution heat treatment and precipitation hardening or aging.Solution heat treatment consists of-heating the metal to a temperatureat which the soluble constituents of the alloy dissolve, holding thematerial at this temperature for a sufficient length of time to allowsubstantially all of the soluble elements or constituents to go intosolid solution and then rapidly quenching .to prevent or retardprecipitation of these constituents from the supersaturated solidsolution. The solution heat treating temperatures of heat treatablealuminum alloys will vary from about 800 to 980 F. depending upon thealloying constituents and their amounts. The precipitation or agehardening treatment follows the solution heat treatment process and iscarried on at either room temperature or at an elevated temperaturedepending on the desired aging time and composition of the alloy. Byprecipitating in a finely dispersed state some of the dissolvedconstituents out of solid solution, the age hardening treatment developsmaximum mechanical properties of the metal.

In the present practice of solution heat treating aluminum alloys thesolution heating is essentially a batch type operation. This practicerequires that the metal be in the form of small units, such asindividual sheets, coils of strip material, coils of wire, etc. Suchprocessing is quite expensive inasmuch as considerable manual labor isrequired, th operation is time consuming, and scrap loss is high. Forexample, one conventional present day practice involves individuallysuspending sheets Within a furnace maintained at a temperature withinthe solution heat treating range for a predetermined period, removingthe heated sheets from the furnace and rapidly quenching the sheets.Such practice results in considerable Warpage and wrinkling of thesheets necessitating a straightening operation. This is generally doneunder tension by clamping each end of the sheet. The clamps employed forsuch straightening operation make clamp marks on the ends or edges ofthe sheet which marks must be eliminated by cutting off that portion ofthe sheet on which the clamp marks appear. This results in edgescrappage which wastes a considerable amount of material and, inaddition, results in a smaller sheet.

Attempts to solution heat treat a coil of strip or wire as a unit arenot generally satisfactory because of the inability to uniformly quenchthe entire coil rapidly "ice enough to retain the constituents in solidsolution. The quenching or cooling medium does not have sufficientaccess to the inner portions of the coiled sheet or Wire.

It has been proposed in the past to solution heat treat continuously byunwinding coiled sheet or wire into a furnace, then through a quenchingmeans and on to a .rewinding wheel. None of these proposals have beensatisfactory when applied to aluminum metal because of several obstaclesthat have not as yet been overcome by the art. In the continuous heattreatment of aluminum sheet, there is a necessity of obtaining a rapidquench in order to have a satisfactory solution heat treat aluminumarticle, since the quenching operation must be very rapid in order toprevent or retard the soluble constituents from coming out of thesolution. In operating a continuous solution heat treating process, thematerial must be in a furnace a sufficient length of time to allowsubstantially all of the soluble constituents to go into solution. Thistime is affected by the speed of the sheet and by the length of travelof the sheet Within the furnace. The metal must pass through the furnaceat a high rate of speed in order to efiect rapid quenching;consequently, the length of travel within the furnace must be great.Horizontally extending furnaces designed to accommodate the great lengthof travel are impractical because of the tremendous amount of floorspace required. Also, one of the chief difliculties in the prior art hasbeen in providing a furnace which uniformly and rapidly heats the metalto the solution heat treating temperature and maintains the metal atthis temperature until substani-ally all the soluble constituent-s gointo solid solution. Various heatin means have been employed for heatingthese large continuous heat treatment furnaces such as, inductionheating, resistance heating, and oil or gas burners. However, none ofthe prior art heating furnaces for continuously heat treating stripmetal have proved successful for commercial adaptation.

Therefore, it is the primary object of this invention to provide animproved method and apparatus for continu ously solution heat treatingelongated heat treatable aluminum alloy members which eliminates orsubstantially reduces the problems associated with methods and apparatusas heretofore known.

It is another object of the invention to provide an improved method andapparatus for continuously heat treating an elongated heat treatablealuminum alloy member whereby the member may be uniformly and rapidlyheated to the solution heat treating temperature and maintained at thistemperature until substantially all the soluble constituents of themetal go into solid solution.

It is a further object of this invention to provide an improved methodand apparatus for continuously heat treating aluminum alloys whereby arapid rate of movemen through the heating Zone is achieved withconsequent rapid quenching without requiring an excessive amount offloor space for the heat treating operation and whereby scarp losses dueto straightening operations are eliminated.

It is also an object of this invention to provide a method and apparatusfor continuously solution heat treating heat treatable aluminum alloyswhereby the metal is heated to the solution heat treating temperature todis solve the soluble constituents in solid solution in the parent metaland whereby said strip is held at said temperature the optimum time andthereafter quenched ra idly enough to prevent precipitation of saidconstituents.

These and other objects are accomplished by the instant invention byproviding a continuous solution heat treating method and apparatuswherein an elongated member of a heat treatable aluminum alloy, such asstrip, sheet and Wire, is rapidly and uniformly heated to the solutionheat treating temperature by conveying the member in ,paratus embodyingthe principles of the invention.

.the sheet of the new coil.

l 3 a tortuous path through a heating furnace comprised of a pluralityof heating chambers, after which the member is passed through a holdingfurnace which is maintained at the solution heat treat temperature ofthe metal. v After passage through the holding furnace, the metal issubjected to rapid quenching means. Means are provided for conveying ahigh velocity heated gas through the tortuous path of the heatingfurnace opposite to the direction of travel of said elongated member insaid heating furnace, thereby rapidly and uniformly heating the metal tothe solution heat treat temperature of the aluminum alloy composition.the heating and holding furnaces at the maximum allowable solution heattreating temperature for the particular metal being treated therebymaintaining the heating and holding furnaces at substantially zero heathead above the solution heat treating temperature. Also, means areprovided for supporting the metal during its passage through the heatingand holding furnaces as well as means for conveying the metal throughsaid furnaces whereby the stress is maintained substantially equalthroughout the length of the metal member within said furnaces and at avalue below the yield strength of the metal at its solution heat treattemperature.

These and various other objects, novel features and advantages of theinvention will become more apparent from a consideration of thefollowing description taken in connection with the accompanying drawingwherein:

FIGURE 1, comprising FIGS. 1A and 1B, illustrates a cross-sectional viewof a solution heat treating ap- Some of the elements of the heattreating apparatus assembly are shown diagrammatically in order tosimplify the drawing.

With reference to the drawing, there is shown a solution heat treatingapparatus for continuously processing a metal member, such as sheet, andwhich is generally comprised of a heating furnace 20, a holding furnace40 comprising an undivided chamber, quenching pit '51, looping towers l8and 65, and superstructure $3. Suit- Means are provided for controllingoperation.

supporting member 16. Each roll 11 isa relatively large driven roll andis positioned adjacent a relatively small rubber covered idler roll 13.One driving roll 11 and one idler roll 13 are hereinafter. referred toas a pair of pinch rolls. The distance between the outer surfaces of thed-rivenroll 11 and theidler roll 13 is somewhat less than thethickness-of the sheet metal 4so that when the metal passes between thepinch rolls the driven roll 11 exerts a force on the strip 4 serving tocontinuously drive the metal through the storage loops and into theheating zone. Looping tower 18 may contain two or more pairs of pinchrolls depending on the metal storage capacity desired. 7

The pinch rolls are capable of being rotated inter- V mittently at highspeed by either automatic controls or by an operator, so that thelooping tower may be filled with sheet after a portion of the sheetstored in the loop ing tower is depleted during the time of the weldingThe pinch rollslzl and 13 control the speed of the sheet in the tower sothat the tower can be filled without changing the speed of the sheet inthe furnace. Although one particular means is shown for storing metal toallow for time for fastening successive coils of sheet metal together,this is given only in the way of example entrance into the furnace. Thesheet-metal will then able accessory equipment for facilitating thecontinuous 7 operation, such as coilers, welders, etc., are also shownand are specifically discussed hereinbelow.

In FIGURE 1A, the coil 1 of sheet metal rests on the coil carriage 2 andis shown in position to be transferred to the coil unwind device 3 whencoil 10, which is shown as being processed through the solution heattreating apparatus, is completely unwound. As coil it) is unwound thesheet metal 4 successively passes through straightening rolls 5 whichflatten the sheet and serve to relieve the curl foundin the sheet causedby coiling.

In order that the operation may be continuous for an indefinite amountof metal, a fastening device, such as a welder 6, is provided wherebythe trailing edge of 'the sheet from a coil being processed may bejoined to the forward edge of the sheet of a new coil. mer 7 is providedto trim off any cracked edges of the sheet thereby preventing a stressconcentration from occurring which could cause the sheet to break withinthe furnace. The scrap from the edge trimming operation is removed fromtrimmer 7 by a suitable scrap conveyor 8. a

An edge trimpass through a pair of sealing rolls 25 and thence throughthe inlet 26 and into'the heating furnace 20. The sealing rolls 25prevent the escape of heated air fromthe heating furnace 20. The sheetmetal 4 enters the heating furnace at the bottom of the "first heatingchamber 27 and travels upward. arounddriven roll 32 and into the secondchamber 39 where it passes down through the second chamber and aroundthe furnace roll 34 and up through the third heating chamber and aroundthe roll 36 after which it passes downward into the final heatingchamber. As the metal sheet 4 travels 'down through the last heatingchamber it travels around the driven roll 37 which in turn directs themetal upward and into the holding furnace 40. The sheet metal 4 thentravels through a tortuous path in a holding furnace 463 by travelingaround a series of driven rolls 33 suitably supported at the top andbottom of the holding furnace.

The several elongated heating chambers of the heating furnace 29 arevertically extending and parallel to each other. Alternate chambers haveopenings 'at the top 7 while the other chambers have openings at thebottom so In order to hold the sheet stationary during the weld- 7 ingoperation a brake 9 is provided to stop the travel of metal through thewelder 6 to allow time for the trailing edge of the sheet to be weldedtothe forward edge of In order not to stop the passage of the sheetthrough the heating and holding furnaces, a suflicient length of sheetmetal is stored in the form of loops 17 in a looping tower 18. Thus, thesheet 4 is stationary during the welding operation atall points to leftof brake 9 as shown in the drawing. T he looping tower 18 is comprisedof a pit 15 into which the loops extend from a group of driven guiderolls 11 which are suitably supported in bearings from a spanv thatthesheet can pass through the chambers in a tortuous path. The holdingfurnace ili is suitably designed so that themetal will remain within itsconfines a suificient time to dissolve in solid solution substantiallyallthe soluble constituents of the metal but yet allow for sufficientspeed of the metal to discharge through outlet 47 and into the sprayingcompartment 49 at a rate sufficient to cool the sheet and initiallyretain the soluble constitucuts in solid solution. a

Y The furnace rolls 32, 34, 36, 37 and 38 are driven at exactly the samespeed at which the strip 4 is traveling through the heating and holdingfurnaces. Each of the furnace rolls is driven individually by a smalldirect current torque motor (not shown), through suitable gear reductiondrive mechanism. These motors are coordimated with a variable Voltagedrive which controls the speed of the strip 4 through the furnace Thepower inputs to the furnace rolls. are designed to be only enough tocompensate for friction lost in "rotating the rolls and for accelerationfrom one speed to another. In other words, there is no pull or dragplaced on the sheet by the furnace rolls. Thus, for example, a giventension or pull put on the sheet at the discharge side would exert thesame tension at the entry side of the furnace. As a consequence, auniform stress on the sheet or strip is maintained throughout the lengthof the sheet within the furnace and the stress is maintained below theyield strength of the metal at its soltuion heat treat temperature.

The furnace rolls are shaped so that the center portion (that is theportion on which the sheet is supported) is slightly larger in diameterthan the ends of the roll. Thus the sheet rides on a crown. The furnacerolls are supported in journals (not shown) which are positioned outsidethe furnace walls.

The metal passes through the outlet 47 of the holding furnace 4i) andinto a spray duct 49 wherein spray nozzles 53 are positioned. Both sidesof the sheet 4 are contacted by the cooling Water from the spray nozzlesthereby quenching the sheet 4 at a rapid rate to approximately roomtemperature. The lower extremity of the duct 49 is submerged below thelevel of the water provided level in a quench tank 54, located inquenching pit 51. Preferably the end of the duct 49 is positioned asubstantial distance below the water level, for example, at least inchesand thus the water serves as a seal to prevent the discharge of heatedgas or air from the discharge side of the furnace. The metal then passesout to the bottom of the spray duct 49 around idler roll 55 and throughthe squeegee rolls 56 which serve to remove excess water from the sheetwhereupon the sheet is passed through a suitable drier, such as amanifold dryer 57.

The sheet metal is next passed through pinch rolls 5d and which conveyor pull the metal sheet through the quenching pit 51 and feed the sheetinto a suitable straightening means such as leveler 61. The pinch rolls59 and 6d at the discharge side of the holding furnace A l and the pinchrolls 21 and 22 at the entry side of the heating furnace 20 control thespeed of the strip through the furnaces. Either the pinch rolls 21 and22 at the entry side of the heating furnace or the pinch roll 5? and 60at the delivery side of the holding furnace will be operated at aconstant speed. Suitable means may be provided whereby the position ofthe dancer roll 23 can regulate the pair of pinch rolls not operating ata constant speed to control the speed of the sheet in the furnace. Theunsupported weight of the dancer roll 23 can be varied to develop thedesired strip tension, eg 115 to 2700 pounds, by using counterweights orother suitable means.

The leveler 61 straightens or flattens the quench warped strip and aidsin relieving quenching stresses set up during the quenching process. Thesheet then passes between pinch rolls 63 and 64- which serve to conveythe sheet into looping tower 65. Two or more sets of these pinch rollsmay be used to form loops and thus store the metal as discussedpreviously in regard to looping tower 43 for storing metal prior to itsentry into the heating furnace 29. On the discharge side of the hold ingfurnace 49, it is necessary that the looping tower 65 be empty or theloops 67 short when the sheet is stopped to cut out the Weld and removethe coil so that the sheet emanating from the furnace til can beaccommodated or stored in the looping tower 65 during the cutting andremoval operations. The sheet 4 passes from the last set of pinch rolls63 and 64 in the looping tower to a set of pinch rolls 69 and 70 whichconvey the sheet metal at floor level to the rewinding operation. Thepinch rolls 69 and 7d at the discharge side of the looping tower 65control the speed of the sheet in the tower so that it can be emptiedregardless of the speed of the strip in the furnace. At this point thesheet metal passes through the super structure 83 and through guiderolls '71 and the shearing device 73. When sufiicient metal is rewound.on the coil to give the desired coil size, the shear-s '73 operate toshear the strip of metal transversely. Preferably the strip is shearedat the weld made by welder .6. A belt wrapper '77 may be used to ensureproper coiling of the sheet.

A super structure $3 which provides a housing for the looping towers andfurnaces, has removable sections to permit access to the looping towers18 and 65, heating furnace 2t holding furnace 4-6 and the equipmentcontained therein. The cat walk 79 across the top of the super structure83 permits access to the rolls in the loop ing towers and the top of theheating furnace 2d and the holding furnace 4t) for maintenance andrepair purposes. A hoist or crane 85 is suspended from the cat walk 79to aid in the replacement of rolls and other equipment in locations notaccessible from the ground level. Bridle supports 31 are disposed 'oneither side of the heating and holding furnaces and attached to thesuper structure 83 at its upper horizontal cross member 79. In order toreduce the height to which the furnaces and looping towers extend abovethe ground level, a pit 15 is provided which contains the looping towersand furnaces.

The inside heating chambers of furnace 26 consists of verticallyextending partition walls or baffles which provide a continuous paththrough the heating furnace. This is accomplished by providing partitionwalls or bafiles 31, 33, 35 and 42 whose length is somewhat less thanthe height of the heating furnace. A passageway is provided betweenadjacent heating chambers, around one end of the partition wall. Sinceadjacent partition walls abut the top and bottom of the furnace,alternately, a tortuous passageway is provided through the heatingfurnace. The adjacent partition walls alternately abut the fioor 24 ofthe heating furnace 2i for example, partition wall 31 and the roof d3(partition walls 33 and 35). Partition wall 35 which extends from theroof 43 of the furnace 20 is the dividing wall between the holdingfurnace 4t) and the heating furnace 2t). Partition walls 31, 33, 35 and42 are supported not only from the top but also from the front and backwalls (not shown) of the furnace by welding. The inner partition wallsor baffles are preferably manufactured from sheet metal, such as 11gauge 430 stainless steel sheet, and are insulated in any suitableinexpensive manner, such as with mineral wool or fiber glass insulation.The insulation may be held in place with a large mesh wire or othersuitable means. The top and bottom of the furnaces are made of removablesections to permit ready access to the rolls and sheet.

The common outer shell of the heating and holding furnaces compriseswalls 29, 4f, 43, 45 plus the front and back walls (not shown). Thisouter shell is welded gas tight to avoid leakage of the recirculatingheated air. Radiation shield 44 is mounted inside of the outer shell andin spaced relationship therewith. Air may be circulated through thespace between the shell and the radiation shield 44 by small circulatingfans (not shown). The air from this space is recirculated by suitablemeans to the heating compartment 87 where it is reheated along with themainstream of high velocity air. This radiation shield construction aidsin maintaining a uniform temperature within the furnaces by minimizingradiation losses to the outside wall and providing for the recirculationand reheating of the coldest air in the furnaces. Thus-the sheet, duringits travel through the heating and holding furnaces, does not face anoutside wall. The temperature of the sheet in the furnace is regulatedby controlling the heated air blown into the furnaces from the heatingcompartment. The air is controlled at the maximum allowable heattreating temperature, and the measurement of the air temperature is asubstantially accurate measurement of the temperature of the sheet. Thismethod of temperature control insures a uniform temperature throughoutthe furnaces. Since there is no point Within either furnace which is ata higher temperature than the heat treating temperature, that is, thereis substantially *Zeroi'heat head in either furnace above the solutionheat treat temperature, it is impossible to.over heat the strip in theevent that the sheet is stopped or 'itsspeed changed. I

The strip 4 is brought up to thesolution heat treating temperatureentirely by circulating, opposite to the direction of travel of thestrip 4, very high velocity heated air in the tortuous path of theheating furnace 20. The air is heated in the heating compartment 87 andblown into the last chamber 89 of the heating furnace 2d by a group ofblowers 91 connected in series. The heating chamber 87 contains radiantheating tubes d3. Hot products of combustion from burners (not shown)pass through the alloy radiant tubes, generally in a U or W fornnand airpasses over the outside of these tubes to pick up the necessary heat.Alternate methods for heating the air would be by passing the productsof combustions directly into the circulating air or by passing the airover electrically heated resistance elements.

An example of discharge of heated air from a heating compartment is40,000 cubic feet per minute at a pressure of approximately 20 inches ofwater. The air circulated by blowers 91 flows in the direction oppositeor countercurrent to the travel of the sheet through the heating furnaceand is exhausted at the charging end 27, and, for purposes ofillustration, may have a velocity of 6000 to 9000 feet per minute.Heating by this means has been found sufficient to permit the speed ofthe sheet traveling through the continuous heat treating furnace to bebetween 40 and 400 feet per minute.

The suction fans 9 recirculate the air from the first chamber 2'7 of theheating furnace Ztl, the recirculated air being taken off at a pointapproximately at the sealing rolls 2:? and recirculated through heatingchamber 87. Circulation of the air around tubes 3 is promoted by battled3 located in heating chamber 87. The base of partition wall 4-2 may besuitably attached to partition wall 31 (rather than floor 24) forsupport (as shown in FIGURE 1A), in order to provide space for exhaustblowers 95. Since the suction side gauge pressure is equal to approximately zero there is little tendency for air to leak either in or out atthe sealing rolls 25. The holding furnace 40 is operated at the inletpressure of the high velocity air which may be on the order of 20 inchesof water, The spray compartment 49 is submerged below the water level inthe quench tank 54- by at least 20 inches so as to seal the dischargeside of the furnace against the operating air pressure.

The holding furnace 4% is maintained at the same temperature as theheating furnace 20 with common heating means by passing a portion of theheated high velocity gas introduced in the heating furnace into theholding furnace. A relatively small amount of hot air is bled oil fromthe large volume of high velocity air llowing into the chamber 89 fromthe beating compartment, through passageway 39, to heat the holdingfurnace lb. 7

Since the stripd is already heated to temperature when it reaches theholding furnace, very little heated air need be added to the holdingfurnacev While an embodiment of my invention has been shown anddescribed, it will be apparent that other adaptations and modificationsmay be made without departing from the'scope of the appended claims.

What is claimed is:

1. Apparatus for continuously solution heat treating an elongated heattreatable aluminum member comprising a heating furnace, a holdingfurnace adiacent said heating furnace, said heating and holding furnaceshaving an outer shell, a radiation shield mounted inside said shell inspaced relationship therewith, partition walls within said heatingfurnace which define a tortuous path, said holding furnace comprising anundivided chamber, common heating means for heating'said aluminum metalmember in saidheating furnace to solution heat treating temperaturewhile maintaining substantially zero heat vertical divided wall betweensaid heating and holding furnaces said wall being provided with anopening to permit passage of said metal member from said heating furnaceto said holding furnace, means within said undivided chamber comprisingsaid holding furnace for supporting said metal member, and means forcontinuously moving said member through said heating and holdingfurnaces while maintaining the stress substantially equal throughout thelength of said metal member in said furnaces and at a value less thanthe yield strength of said metal member. 2. Apparatus for continuouslyheat treating an elongated heat treatable aluminum alloy membercomprising a heating furnace, a holding furnace adjacent said heatingfurnace, said heating and holding furnaces having an outer shell, aradiation shield mounted inside said shell in spaced relationshiptherewith, partition walls within said heating furnace Whichdefine atortuous path, said holding furnace comprising an undivided chamber,common heating means for heating said aluminum metal member in saidheating furnace tosolution heat treating temperature while maintainingsubstantially zero heat head in the furnace above the solution heattreating ternperature and for maintaining said holding furnace also atsaid temperature, said common heating means comprising means forconveying high velocity heated gas both along said tortuous path in saidheating furnac in a directionopposite to travel of said metal member andinto the undivided chamber comprising said holding furnace, a pluralityof driven rolls within said'heating and holding furnaces for supportingsaid member during travel therethrough, said holding furnace beingadapted to receive said member as it emerges from said heating furnaceand being of sufficient capacity to hold said member at the solutionheat treating temperature of said member for a time sufiicient to allowsubstantially all of the alloy constituents to go into solid solution, avertical, insulated, dividing wall between said heating and hold ingfurnaces, said wall being provided with an opening at its lowerextremity for a passage of said member, means for continuously movingsaid member through said heating and holding furnaces while maintainingthe stress substantially equal throughout the length of said' memberwithin said heating and holding furnaces and at a value less than theyield strength of said member, means for quenching said member asitemerg-es from said holding furnace, means for removing excess waterfrom said member as it emerges from said quenching means, means fordrying said member, and means for continuously straightening said memberafter it has been quenched and dried. T p v 3. Apparatus for.continuously heat treating an elongated heat treatable aluminum alloymember comprising a heating furnace, a holding furnace adjacentsaidheating furnace, said heating andholdingfurnaces having an outer shell,a radiation shield mounted inside said shell in spaced relationshiptherewith, partition walls within said heating furnace which define acontinuous tortuous path, said holding furnace comprising an undividedchamber, common heating means for 'he-ating'said aluminum metal memberin said heating furnace to solution heat treating temperature whilemaintaining substantially zero heat head in the furnace above thesolution heat treating temperature and for maintaining said holdingfurnace also at said temperature, said common heating means comprisingmeans for conveying high velocity heated gas both along said tortuouspath in said heating furnace in a direction opposite to travel of saidmetal member and into the undivided chamber comprising said holdingfurnace, external pinch roll means for controlling the speed of saidelongated member through said heating and holding furnaces, a pluralityof internal rolls Within said heating and holding fuurnaces forsupporting said member during travel therethrough, said internal rolls'being driven at exactly the same speed as said elongated member asdefined by said external roll means whereby the elongated member iscontinuously moving through said furnaces while the stress is maintainedsubstantially equal throughout the length of said member within saidfurnaces and at a value less than the yield strength of said member,said holding furnace being adapted to receive said member as it emergesfrom said heating furnace and being of suflicient capacity to hold saidmembet at the solution heat treating temperature of said mem- 'her for atime sufiicient to allow substantially all of the alloy constituents togo into solid solution, a vertical, insulated, dividing Wall betweensaid heating and holding furnaces, said Wall being provided with anopening at eases its lower extremity for the passage of said member,means for quenching said member as it emerges from said holding furnace,means for removing excess water from said member as it emerges from saidquenching means, means for drying said member, and means forcontinuously straightening said member after it has been quenched anddried.

References Cited by the Examiner UNiTED STATES PATENTS 2,104,518 1/38Hoak 266-3 2,232,391 2/41 Keller 266-3 X 2,669,442 2/54 Erhardt 2663 X2,693,353 11/54 Vaughan 266-3 2,887,422 5/59 Stone et a1. 148-1592,926,902 3/60 Roth 2663 2,991,989 7/61 Martin 263--3 FOREIGN PATENTS801,363 9/ 58 Great Britain.

MORRIS O. WOLK, Primary Examiner.

RAY K. WINDHAM, MARCUS U. LYONS, Examiners.

1. APPARATUS FOR CONTINUOUSLY SOLUTION HEAT TREATING AN ELONGATED HEATTREATABLE ALUMINUM MEMBER COMPRISING A HEATING FURNACE, A HOLDINGFURNANCE ADJACENT SAID HEATING FURNACE, SAID HEATING AND HOLDINGFURNANCES HAVING AN OUTER SHELL, A RADIATION SHIELF MOUNTED INSIDE SAIDSHELL IN SPACED RELATIONSHIP THEREWITH, PARTITION WALLS WITHIN SAIDHEATING FURNACE WHICH DEFINE A TORTUOUS JPATH, SAID HOLDING FURNACECOMPRISING AN UNDIVIDED CHAMBER, COMMON HEATING MEANS FOR HEATING SAIDALUMINUM METAL MEMBER IN SAID HEATING FURNACE TO SOLUTION HEAT TREATINGTEMPERATURE WHILE MAINTAINING SUBSTANTIALLY ZERO HEAT HEAD IN THEFURNANCE ABOVE THE SOLUTION HEAT TREATING TEMPERATURE AND FORMAINTAINING SAID FOLDING FURNACE ALSO AT SAID TEMPERATURE, SAID COMMONHEATING MEANS COMPRISING MEANS FOR CONVEYING HIGH VELOCITY HEATED GASBOTH ALONG SAID TORTUOUS PATH IN SAID HEATING FURNACE IN A DIRECTIONOPPOSITE TO TRAVEL OF SAID METAL MEMBER AND INTO THE UNDIVIDED CHAMBERCOMPRISING SAID HOLDING FURNACE, MEANS WITHIN SAID HEATING FURNANCE FORSUPPORTING